How to print words using reverse_iterator in STL - c++

Question

I have to read two text files and then compare words from second file with the first one. Then , I have to display KnownWords which are same words from both files and the remaining words which are not same are UnknownWords. Next Step is, I have to display most frequent known words in DisplayMostFreqKnownWords() and unknown words in DisplayMostFreqUnknownWords() functions. I have successfully completed DisplayMostFreqKnownWords() and so far Output is alright. I copied the same code from DisplayMostFreqKnownWords() to DisplayMostFreqUnknownWords() but in this is function it is not showing anything in the output. I dont know what is wrong. Can someone figure this one out.
Output is:
Displaying most frequent known words
Word Count
the 19
a 14
of 11
artificial 11
that 10
to 7
signal 7
and 7
in 6
they 5
Displaying most frequent unknown words
Word Count
Header file:
typedef map<string, vector<int> > WordMap;
typedef WordMap::iterator WordMapIter;
class WordStats
{
public:
WordStats();
void ReadDictionary();
void DisplayDictionary();
void ReadTxtFile();
void DisplayKnownWordStats();
void DisplayUnknownWordStats();
void DisplayMostFreqKnownWords();
void DisplayMostFreqUnknownWords();
private:
WordMap KnownWords;
WordMap UnknownWords;
WordMapIter Paragraph;
set<string> Dictionary;
char Filename[256];
}
My program:
// Displays 10 most frequent words in KnownWords
void WordStats::DisplayMostFreqKnownWords(){
int count;
multimap<int,string > displayFreqWords;// new map with int as key
(multimap because key could occur more than once)
multimap<int,string >::reverse_iterator rit = displayFreqWords.rbegin();
for (Paragraph = KnownWords.begin(); Paragraph != KnownWords.end();
++Paragraph){ // iterate map again
string word = (*Paragraph).first;
int cnt = (*Paragraph).second.size();
displayFreqWords.insert(pair<int,string>(cnt,word));
}
// multimap<int,string>::iterator rit; // iterator for new map
cout <<" Word Count\n";
for(; count<=10 && rit!=displayFreqWords.rend(); rit++, ++count){
string word = (*rit).second;
int cnt = (*rit).first;
cout << setw(15) << word << setw(10) << cnt << endl;
}
}
// Displays 10 most frequent words in UnknownWords
void WordStats::DisplayMostFreqUnknownWords(){
int count;
multimap<int,string > displayFreqUnknownWords;
multimap<int,string >::reverse_iterator rrit =
displayFreqUnknownWords.rbegin();
for (Paragraph = UnknownWords.begin(); Paragraph !=
UnknownWords.end(); ++Paragraph){
string word = (*Paragraph).first;
int cnt = (*Paragraph).second.size();
displayFreqUnknownWords.insert(pair<int,string>(cnt,word));
}
// multimap<int,string>::iterator rit; // iterator for new map
cout <<" Word Count\n";
for(; count<=10 && rrit!=displayFreqUnknownWords.rend(); rrit++, ++count){
string wrd = (*rrit).second;
int ccnt = (*rrit).first;
cout << setw(15) << wrd << setw(10) << ccnt << endl;
}
}

Answer 1

Here's a way to express what I think is your use case. I have used c++17 tuple expansion.
I have used unordered_map to deduce which words are known or unknown, and two multimaps to determine known and unknown word frequency.
Hope it's helpful.
#include <sstream>
#include <tuple>
#include <string>
#include <unordered_map>
#include <algorithm>
#include <iterator>
#include <map>
#include <iostream>
#include <iomanip>
#include <fstream>
// Set this to 1 to run a static test
#define TESTING 0
#if TESTING
using input_type = std::istringstream;
std::tuple<input_type, input_type> open_inputs() {
return {
std::istringstream("the big black cat sat on the grey mat"),
std::istringstream("the gold small cat lay on the purple mat")
};
}
#else
using input_type = std::ifstream;
std::tuple<input_type, input_type> open_inputs() {
return {
std::ifstream("left_file.txt"),
std::ifstream("right_file.txt"),
};
}
#endif
struct Counts {
int left_count = 0, right_count = 0;
int total() const {
return left_count + right_count;
}
bool is_known() const {
return left_count && right_count;
}
};
template<class F>
void for_each_word_in_file(std::istream &is, F f) {
std::for_each(std::istream_iterator<std::string>(is),
std::istream_iterator<std::string>(),
f);
}
int main() {
// open files
auto[left, right] = open_inputs();
auto known_words = std::unordered_map<std::string, Counts>();
// count words in each file
for_each_word_in_file(left, [&known_words](auto &&word) {
++known_words[word].left_count;
});
for_each_word_in_file(right, [&known_words](auto &&word) {
++known_words[word].right_count;
});
// map counts to words, in descending order, allowing multiple entries of the same count
std::multimap<int, std::string, std::greater<>> known_ordered, unknown_ordered;
// iterate all words seen, putting into appropriate map
for (auto&&[word, counts] : known_words) {
(counts.is_known() ? known_ordered : unknown_ordered)
.emplace(counts.total(), word);
}
// emit results
std::cout << "Known words by frequency\n";
for (auto&&[freq, word] : known_ordered) {
std::cout << std::setw(15) << word << " " << freq << '\n';
}
std::cout << "\nUmknown words by frequency\n";
for (auto&&[freq, word] : unknown_ordered) {
std::cout << std::setw(15) << word << " " << freq << '\n';
}
}